Capital Cities

This prolonged lock down has led to Dr Zonga studying maps and dreaming of exploring once again...  In his dreaming, Dr Zonga came up with the question: 

Which two capital cities, with the same starting letter, are closest to each other.  

For example, Brussels and Bangkok both start with B.  They are 9259km from each other. Can you beat that?  

If you have a good answer, drop it through to dean@DrZonga.com 

Or compare with others' answers here